I'm attempting to set up the VSI plugin for Vsphere/Vcenter after we recently installed a new Dell Powerstore storage appliance.  On the Register Vcenter Server(s) portion I have entered both my domain user/name and password (has admin rights on Vcenter server) as well as the local administrator@vsphere.local username and password; I've also entered our Vcenter server information using the FQDN as well as IP address. I keep getting the following error:

"Unable to login to vCenter, please validate the username, password and vCenter are correct. If the problem persists please check the NTP settings on your vCenter for clock skew error."

I have verified NTP services are working on our Vcenter server, time on hosts are sync'd. 

Any help is appreciated

-Drew Parker